The overall goal of this project is to delineate the role of hormonal factors in the metabolic and functional response of skeletal muscle during and following exercise. Ongoing studies utilizing a perfused rat hindquarter preparation have demonstrated that epinephrine is needed for the maintenance of muscle glycogenolysis after the first few minutes of exercise. In addition, it increases oxygen consumption and diminishes fatigue, particularly when the muscle is inadequately oxygenated due to a low flow rate. We are now exploring the mechanism for these effects, as well as the effects of epinephrine on different fiber types. We are also evaluating the effect of insulin on the metabolism of muscle following exercise using the perfused hindquarter preparation. We have shown that the sensitivity of muscle to insulin as judged by insulin's ability to stimulate glucose transport is increased and we are presently exploring the mechanism for this effect. In addition, we will assess whether processes other than glucose transport and tissues other than muscle also become more sensitive to insulin.